Synthesis and characterization of a novel Schiff-base/SBA-15 nanoadsorbent for removal of methylene blue from aqueous solutions

Abstract

A novel Schiff-base/SBA-15 nanoadsorbent was successfully synthesized by the reaction of salicylaldehyde and (3-aminopropyl) trimethoxysilane in methanol and subsequent grafting with SBA-15. The morphology and structures of the as-synthesized Schiff-base/SBA-15 nanoadsorbent were characterized by powder X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, thermo-gravimetric analysis, and N2 adsorption/desorption isotherms. The obtained Schiff-base/SBA-15 nanoadsorbent was used for the removal of methylene blue (MB) from aqueous solutions. The effects of various parameters such as temperature, concentration, pH, and contact time were examined, and optimal experimental conditions were determined. The equilibrium isotherms were conducted using Freundlich and Langmuir models. The pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to fit adsorption data in the kinetic studies. The thermodynamic parameters such as the standard enthalpy, standard entropy, and standard free energy were evaluated. The obtained results indicated that the Schiff-base/SBA-15 nanoadsorbent is an efficient adsorbent for removing MB.